Coating thickness control mechanism



Fe 20, 1962 M. HEGYI 3,022,011

COATING THICKNESS CONTROL MECHANISM Filed Oct. 9, 1959 3 M Q 1%? I, a Z6 i 66 I --70 i j 52 400 54 O a I 0 6%; l 50 a 45 o i 12 fnz/erzz bf M0565 fi e gyzl United States Patent Office 3,622,611 Patented Feb. 20, 1962 3,022,011 COATING THICKNESS CONTRQL MECHANISM Moses Hegyi, Orland Park, 111., assignor to Borg-Warner Corporation, Chicago, Ill., a corporation of Illinois Filed Oct. 9, 1959, Ser. No. 845,391 12 Claims. (Cl. 239-97) This invention relates to automatic spray coating equipment and particularly to vertically reciprocating paint spraying equipment.

For coating sizable sheets of material such as steel of the order of four to sis feet in width, for example, it is conventional practice to use a paint spraying apparatus which has mounted thereon a vertically reciprocating paint spray gun. A length of this material to be coated may be supported vertically and moved relatively to the paint spray apparatus. Either the apparatus may be held stationary and the material to be coated moved past the apparatus or the material may be held stationary and the apparatus moved past the material. In either event, however, a spray gun forming part of the apparatus is generally moved up and down to cover the total width of the work to be sprayed. Generally, the paint spray gun is fed from a paint tank which may be under pressure to assist in forcing the paint through the nozzles of the spray gun. Such a tank is sometimes located remotely at a distance from the paint spray apparatus itself and may, for example, be supported from a ceiling structure. In any event, in addition to the pressure which may be applied to the spray tank as pointed out above, there exists at the nozzles of the spray gun a hydrostatic pressure (which varies with the different position of the spray gun), i.el, the hydrostatic pressure is lower when the spray gun is at a relatively high point in its vertical path of travel and higher when the "spray gun is at a relatively low point in its path of travel. The variation in hydrostatic pressure with the change in height of the spraying apparatus results in a greater or lesser volume of liquid being emitted from the spray nozzles depending on the relative height of the spray nozzles, i.e., more paint is emitted with a greater hydrostatic pressure and a smaller quantity is emitted with a lesser hydrostatic pressure. This results in a variation in thickness in the coating deposited on the material assuming that the paint spray gun is moved up and down at a constant speed. It has been determined, for example, that where a sheet of material of the order of five to six feet in width is to be coated, that there may be a variation of 303-304 inches in the thickness of the coating applied, that is, that the coating at the bottom of the sheet will be .0O3.004 thicker than at the top of the sheet because of the difference in hydrostatic pressure on the paint spray gun at its upper and lower positions.

Since the spray gun moves continuously with an up and down reciprocating movement, it has been determined that if the speed of travel of the spray gun could be decreased as the hydrostatic pressure was decreased and increased as the hydrostatic pressure was increased, that a substantially even coating could be applied on the material in spite of the different quantities of paint emitted due to the variation in hydrostatic pressure during the up and down movement of the spray gun.

Accordingly, one of the objects of this invention is to provide a mechanism which will deposit an even coating at all stages of the varying height of the spraying apparatus.

Another object of this invention is to provide a mechanism whereby the variable speed of the spraying apparatus is utilized to compensate for the diiference in hydrostatic pressure at various positions of the spraying apparatus in its vertical path of travel.

Another object of this invention is to provide a variable speed mechanism which is responsive to the vertical movement of the spray gun carriage to control the amount of paint or other coating material which may be emitted from the spraying apparatus. A still further object is to provide a mechanism wherein the travel of the spray gun carriage actuates a cam eclianisrn for varying the speed of the carriage itself. A still further object is to provide a mechanism where- 111 the spray gun carriage actuates a cam mechanism which in turn acts to vary the pitch of a variable speed drive pulley so as to vary the speed of the spray gun carriage thereby varying the amount of coating deposited during the travel of the spray gun carriage.

These and other important objects of the invention will be more clearly understood upon reading the following detailed description and reference to the accompanying drawings wherein:

FIG. 1 is a side view of a paint spraying apparatus;

FIG. 2 is a top view of the apparatus taken along the line 2r2 of FIG. 1;

FIG. 3 is a front view of a portion of the paint spraymg apparatus taken along the line 33 of FIG. 1;

FIG. 4 is a detail of the adjustable cam track;

FIG. 5 is a detail of the variable pitch pulley used for driving the spray gun carriage.

Referring now to the drawings wherein like reference numerals are used to indicate similar parts throughout the various figures, the numeral 10 indicates generally a paint spray unit. The unit 10 comprises a frame 12, a spray gun carriage 14 carrying a spray gun 15. The spray gun carriage 14 is mounted for vertical reciprocatmg movement on the vertical guide bars 16 and 18. The unit 10 also comprises a drive base 20. Suitable fluid connections are made to the spray gun 15 in a conventional manner, the fluid being supplied through a conduit 19 connected with a uniformly pressurized paint tank (not shown). The frame 12 comprises a base 22 on which are mounted the vertical guide bars 16 and 18. Also mounted on the frame 12 is a vertical member 24, the top portion 26 thereof being used to guide a slide cam eclianism which will be hereinafter more fully described. Attached to the base 22 are brackets 28 and 36 which carry a pair of bars 32. The drive base 20 carries a pair of brackets 34 and 36 which are adapted to be slidably mounted on the bars 32 so that the drive base it? may slide back and forth relative to the frame 12. It will be appreciated that other means, such as rollers, may be used to mount the driv bas 29 on the frame 12 to permit relative motion of the drive base 20 with relation to the frame 12.

A drive motor 38 is mounted on the drive base 29 and is connected by a belt drive 4% to the spray gun carriage 14 through a speed reducer unit 42 and a chain drive 44, the chain drive being drivingly connected to the spray gun carriage 14 Attached to ad driven by the drive motor 38 is a variable pitch pulley 46 having a stationary member 48 and a movable member 56 which are mounted on a motor drive shaft 52. Th movable member 59 has attached thereto a collar 54. A huhmember 56 is fixedly mounted on the drive shaft 52 by means of a key or other conventional arrangement so that the hub member 56 is stationary with respect to the drive shaft 52. A compression spring 58 is positioned between the movable member 5i and the hub member 56. The members 48 and 59 of the variable pitch pulley 46 are formed to accommodate a V-belt. The speed reducer unit 42 has mounted thereon a shaft 66 on which is mounted a fixed pulley 52 which is driven by the motor 38 and the pulley 46. The speed reducer unit 42 has an output shaft 64 which is drivingly connected to a drive sprocket 66.

a 80 has formed thereon a cam surface 82.

Another sprocket wheel 63 is rot"tahly mounted at the upper portion of the vertical member 2-4. The two sprocket wheels 66 and 68 accommodate the drive chain 76. The chain drive mechanism 44 is provided with a conventional arrangement (not shown) for forming the driving connection between the drive chain 70 and the spray gun carriage 14 and for permitting the spray gun carriage to travel in the same vertical plane when it reverses its direction of movement.

A cam mechanism 74 is adiustably mounted on the drive base and coacts with a cam roller mounted on the spray gun carriage 14 as hereinafter described. The cam mechanism 74 comprises a fixed substantially vertical arm 76 attached to the driv base at 7 8. The cam mechanism 74 also comprises a cam bar 80. The cam bar A bracket 84 is fixedly attached to the cam bar 80 at 86 and is adjustably attached to the arm 76 by means of a bolt 88 which is received by a slot 99 formed in the bracket 84. The lower portion of the cam bar 80 is adjustably secured to the drivebase 20 by means of two bolts 92 and 94. Slots 96 and 98 are provided in the cam bar 80 respectively for the bolt connections 92 and 94. The adjustable bolt connections 88, 92 and 94 permit adjustment of the cam bar 80 to various inclined positions relative to the plane of movement of the spray gun a carriage 14. The upper portion of the cam bar 80 has formed thereon a depending lip 100 adapted to slidably move in the groove 102 formed in the upper portion of the vertical member 24. Attached to the spray gun carriage 14 is a bracket 104 carrying a cam roller 106 which is adapted to coact with the cam surface 82 of the cam bar 80.

A tension spring 108 is attached to the bottom portion of the vertical member. 24 and the bracket 36 which is attached to the drive base 20.

A compression spring 110 surrounds the vertical guide bar 16 so as to be positioned between the spray gun carriage 14 and the base 22.

Operation When the drive motor 38 is running a drive is completed through the variable pitch pulley 46, the V-belt drive 40,

the fixed pulley 62, the speed reducer unit 42 to the.

sprocket wheel 66. Thus the drivechain 7 i) is driven and carries with it the spray gun carriage 14. The carriage 14 is carried upwardly to the top of the unit and then back down as the endless chain is continuously driven by the drive sprocket 66. During the upward. travel of the carriage 14 the bracket 104 and the cam roller 106 are obviously carried with it. During this upward movement the cam roller 106 bears against the cam surface 82. The cam bar 80,'as shown in FIG. 1, is slightly inclined to the right, the proper adjustment of the bolt connections 88, 92 and 94 having been made to set the desired inclination of the cam bar. Thus, as the cam roller 106 moves upwardly, the drive base 20 to which the cam bar 80 is attached moves to the left as shown in FIG. 1 against the tension exerted by the spring 108. As this drive base 26 moves to the left, a tension is put on the V-belt so and decrease the pitch of the variable pitch pulley 46.

This decreasing of the pitch takes place by the V-belt tightening up and slipping down between the stationary member 48 and movable member 50 of the pulley 46. It will be noted that'due to the inclination of the cam bar 80, thedrive base 20 will be progressively moved to the left as seen in FIG. 1 as the cam roller 106 moves upward. Thus, the pitch of the pulley 46 will be constantly decreased throughout the entire upward movement of the carriage of the cam roller 106. As the pitch of the pulley '46 is decreased the speed of the reducer unit is necessarily decreased with a consequent decrease in the speed of the drive sprocket and the drive chain connected thereto. Thus it will be seen that the carriage 14 attains its slowest rate of movement as it approaches the upward portion of its path of travel.

As the carriage commences its downward path of travel, the tension spring 108 will tend to return the drive base to its original position, that is, move it to the right as seen in FIG. 1, and the tension on the belt drive 40 will be decreased. This decrease in tension on the belt drive will permit the variable pitch pulley, through the expansion of the compression spring 58, to increase its pitch and thus increase the speed of the speed reducer unit 42 and consequently the speed of the spray gun carriage 14 as it moves to a lower position. It will be noted that both the tension spring 108 forming a connection between the drive base 20 and the vertical member 24 of the frame 12 and the spring 58 associated with the variable speed pulley assist the drive base 20 in moving to the right as shown in FIG. 1.

During downward movement of the spray gun carriage 14, there is sometimes a tendency for the carriage to pick up additional speed'due to gravity unless means are provided to eliminate this undesirable efieot. To insure that the movement of the carriage 14 is due solely to the chain drive, cushioning compression springs 110 may be mounted on the vertical bars 16 and 18 or on only one of those bars. Such a spring in its expanded form may extend, for example, half the height of the unit. Such a spring has a gradual cushioning effect on the carriage during its downward travel and decreases the effect of gravity on the carriage. This, therefore, helps to insure that the speed of the carriage is controlled solely by the speed of the drive chain.

As previously indicated, when the spray gun moves downwardly, the hydrostatic pressure progressively increases and becomes greatest when the spray gun. is at its lowest position as shown in FIG. 1. Consequently, a greater emission of coating material results because of this increased hydrostatic pressure. Conversely, a lesser emission of coating material occurs with a decrease in hydrostatic pressure. In order to overcome this problem, this device has been designed so that the speed of travel of the spray gun'will be progressively decreased during its upward travel and progressively increased during its downward travel to compensate for the greater emission of fluid and lesser emission of fluid due to variation in hydrostatic pressure while moving downwardly and upwardly respectively. This compensation results in eliminating an undesirable variation in the thickness of the coating so that instead of having a variation of .003- .004 inches in coating thicknessbetween the top and bottom of a sheet 5-6 feet wide, the variation can be kept within a tolerance of less than .001 inch.

In summary, it can be seen that this device provides a very simple method for compensating for the variation in the thickness of a coating deposited by a spray gun where variations in hydrostatic pressure vary the thickness of the coating depending upon the height of the spray gun. This is advantageously.accomplished by the use of a variable speed drive comprising, in this case, a variable pitch pulley acting in conjunction with a cammed device actuated by the movement of the spray gun carnage.

While the foregoing paragraphs and accompanying drawings have disclosed a particular embodiment of the invention, it is to be understood that these disclosures are for the purpose of description only and the invention shall be limited only by the scope of the appended claims.

I claim: a

1. In a vertically reciprocating system including a coating device means. for compensating for variable hydrostatic pressure on said device, said means including a variable speed drive which regulates the rate of upward and downward movement of said device so that said rate is proportional to said hydrostatic pressure.

2. In a vertically reciprocating paint spraying system, a spraying device responsive to hydrostatic pressure, means for controlling the thickness of paint sprayed on an article being painted including a variable pitch pulley drive and means actuated by saidspraying device for varying the pitch of said pulley drive.

3. In a vertically reciprocating coating system a coating device which moves in a substantially vertical plane and is responsive to hydrostatic pressure means for controlling the rate of travel of said device so that the rate of travel is directly proportional to the hydrostatic pressure on said device.

4. The device of claim 3 wherein the means for controlling the rate of travel includes a variable pitch pulley drive.

5. The device of claim 3 wherein the means for controlling the rate of travel includes a variable pitch pulley drive, and means for varying the pitch of said pulley drive including a cam mechanism actuated by the move ment of said coating device.

6. The device of claim 3 wherein the means for controlling the rate of travel includes a variable pitch pulley drive, means for varying the pitch of said pulley drive including a cam mechanism actuated by the movement of said coating device, said cam mechanism comprising an inclined bar.

7. The device of claim 6 wherein the inclined bar of the cam mechanism is adjustable to increase or decrease the rate of acceleration or deceleration of the coating device.

8. In a continuous spray coating device adapted for spraying paint wherein the hydrostatic pressure head of the paint at the spraying device varies with the changing height of the spraying device during the course of its up and down movement the combination comprising: a frame member, a spray gun carriage mounted on said frame, an endless chain drive for moving said carriage up and down on said frame, a drive base movably mounted on said frame and carrying a drive motor, a speed reducer unit mounted on said frame and drivingly connected to said chain drive, a variable pitch pulley drive arrangement between said drive motor and said speed reducer unit for varying the speed of. said chain drive and the spray gun carriage drivingly connected to said chain drive, and means actuated by said spray gun carriage for varying the pitch of said pulley and thereby the speed of said chain drive.

9. In a continuous spray coating device adapted for spraying paint wherein the hydrostatic pressure head of the paint at the spraying device varies with the changing height of the spraying device during the course of its up and down movement the combination comprising: a frame member, a spray gun carriage mounted on said frame, an endless chain drive for moving said carriage up and down on said frame, a drive base movably mounted on said frame and carrying a drive motor, a speed reducer unit mounted on said frame and drivingly connected to said chain drive, a variable pitch pulley drive arrangement between said drive motor and said speed reducer unit for varying the speed of said chain drive and the spray gun carriage drivingly connected to said chain drive, and means actuated by said spray gun carriage for varying the pitch of said pulley and thereby the speed of said chain drive, said means including a cam track mounted on said drive base, the movement of said drive base being responsive to the up and down movement of said spray gun carriage in contact with said cam track.

10. In a continuous spraying device adapted for spraying paint wherein the hydrostatic pressure head of the paint at the spraying device varies with the changing height of the spraying device during the course of its up and down movement the combination comprising: a

frame member, a substantially vertical track mounted on said frame member, a carriage mounted on said track for up and down movement along said track, a chain drive connected to said carriage, a spraying device carried by said carriage, a drive base movably mounted on said frame, a drive motor mounted on said drive base, a speed reducer unit driven by said motor and connected to said chain drive for driving said chain drive, a variable pitch pulley arrangement between said drive motor and said speed reducer unit, an adjustable cam track mounted on said drive base, a cam roller connected to said carriage for coacting with said cam track when said carriage and spraying device are moved along said vertical track, said cam roller being effective to move said drive base and the motor mounted thereon to vary the pitch of said pulley and thereby change the speed ratio between the motor and speed reducer to cause a deceleration of the carriage and spraying device during upward movement thereof and acceleration during downward movement thereof.

11. In a continuous spraying device adapted for spraying paint wherein the hydrostatic pressure head of the paint at the spraying device varies with the changing height of the spraying device during the course of its up and down movement the combination comprising: a frame member, a substantially vertical track mounted on said frame member, a carriage mounted on said track for up and down movement along said track, a spraying device carried by said carriage, a drive base movably mounted on said frame, a drive motor having a drive shaft mounted on said drive base, a variable pitch pulley mounted on said drive shaft, an endless chain drive for driving said carriage, a speed reducer unit driven by said motor by a belt drive and connected to said chain drive for driving said chain drive, a cam track mounted on said drive base and actuated by said carriage during its movement along said track to move said drive base and the motor mounted thereon thereby tensioning the belt drive so as to decrease the pitch of said variable pitch pulley and thereby reduce the speed ratio between the motor and speed reducer thus causing a constant deceleration of the carriage and spraying device during upward movement thereof, and spring means connecting said frame and said drive base to facilitate return of the drive base to its normal position during downward movement of said carriage thus increasing the pitch of said variable pitch pulley and the speed ratio between the motor and the speed reducer thus causing a constant accelerated downward movement of the carriage and spraying device.

12. In a continuous spraying device adapted for spraying paint wherein the hydrostatic pressure head of the paint at the spraying device varies with the changing height of the spraying device during the course of its up and down movement the combination comprising: a frame member, a substantially vertical track mounted on said frame member, a carriage mounted on said track for up and down movement along said track, a spraying device carried by said carriage, a drive base movably mounted on said frame, a drive motor having a drive shaft mounted on said drive base, a variable pitch pulley mounted on said drive shaft, an endless chain drive for driving said carriage, a speed reducer unit driven by said motor and connected to said chain drive for driving said chain drive, an adjustable cam track mounted on said drive base, a cam roller connected to said carriage for coacting with said cam track when said carriage and spraying device are moved along said vertical track, said cam roller being effective to move said drive base and the motor mounted thereon in a direction away from said speed reducer unit so as to decrease the pitch of said variable pitch pulley and thereby reduce the speed ratio between the motor and speed reducer thus causing a deceleration of the carriage and spraying device during upward movement thereof, first spring means connecting said frame and said drive base to facilitate return of the ment qf the'carriage to be controlled entirely by the chain drive.

References Cited in the file of this patent UNITED STATES PATENTS Ballew July 25, 1950 Verba June 24, 1958 Verba June 24, 1958 

